unsaturated polyester resins

The Manufacturing Process Of FRP And How Polyester Resin Can Help In It

You can evidently, discover the polyester resin for FRP products in any industry and its various applications. For instance, you will see many stairways and attractions constructed from FRP when you move to a water park. If you explore a brewery, you can see the catwalks and scaffolding generally made up of FRP.

Fiberglass is ideal everywhere because of its versatility and long-lasting material accessible for structures and other applications such as flooring and wall coverings. And to learn precisely about how FRP is made, you must know initially about the unsaturated polyester resins, and this article will assist you in doing it.

What is FRP:

Polyester resin for FRP is a composite fabricated up of resins (thermosetting) and fiberglass, which are ultimately delicate glass fibers. These glass fibers and the multiple resins it is integrated make up the base agents of FRP products. However, the resins contribute to the numerous chemical and environmental resistance qualities and cover the glass fibers’ 

inside the structural layer. Therefore, manufacturers make the product which is typically composed of three layers, also specified as laminates.

  • Structural layer: This layer is for structural integrity and temperature resistance
  • Surface veil (topcoat): This layer is specifically for environmental and temperature resistance.
  • The chemical barrier layer (CBL):  This layer offers chemical resistance that provides FRP products their anti-corrosive feature.

As evident, the composite’s highlighting is on the durability and structural strength irrespective of any environment. When you learn about how FRP is fabricated, it is a very influencing case for widespread usage in multiple industries due to its benefits.

Pultrusion is the key:

Most of the FRP products from manufacturers are constructed by employing the process of pultrusion. Due to the inheritance of the pultrusion process, this procedure offers multiple benefits over other procedures, such as higher corrosion resistance, better impact resistance, and increased strength.

What is pultrusion:

Pultrusion is a construction process that generates continuous polymer structural shapes that possess consistent cross-sections for higher strength. The name itself suggests a machine ‘pulls’ the raw materials with the help of a linear process utilizing a continual pulling mechanism. In this case, the raw materials are the resin combination in liquid form filler, resin, and application-specific additives, and the glass fibers that offer the reinforcement. The fiberglass is irregular forms, spools of fiberglass filaments and rolls of fiberglass mat similar to fine strands.

Polyester resin for FRP basics:


Reinforcement fiberglass (materials) are removed through the line and soaked in a resin bath until entirely soaked.

Step: 2

A surfacing topcoat (veil) is added according to the requirements of the project.

Step: 3

After it gets soaked, the composite is removed with the help of a pre-former which assembles it for the heated steel die. Moving through this die is what cures or hardens the composite and formulates it to the shape of the die.

Step: 4

The hardened shape is then removed through the last stage, which is the chop-off saw.

The critical role of the materials:

A fiberglass product is constructed for different environments and applications; multiple materials can be utilized to make the final product meet several specifications.


Resins offer chemical and environmental resistance to the finished product and are the binding compound of the glass fibers. Manufacturers apply distinct variations of resins based on the environment the products will be utilized in and the traits described by the customers, such as:

  • Environmental temperature resistance
  • Corrosive/chemical resistance
  • Flame retardancy
  • Heat distortion temperature (HDT)

When selecting the resins for a specific fabrication, there are three main categorizations used in FRP fabrication.

Polyester resins:

Polyester resin for FRP is commonly used nowadays in the industry, maximizing the sale of the businesses. Polyester is a liquid adhesive resin integrating monomer and polyester solution, generally styrene. These resins are so familiar because they cure fast, tolerate extreme temperatures and catalysts, and, most above they are easy to use. There are two distinct types of polyester resin; Isophthalic resin is commonly preferred in industries like off-shore drilling because of its exceptional water resistance. And Orthophthalic resin is typically the most often used variation.

Epoxy resins:

Epoxy resin is most often utilized in fabricating products with an increased level of strength. Apart from the highest strength, epoxies surpass the other resins in bonding and stability with other materials. Recently, epoxy is the most advanced resin and needs consistent accuracy in handling and measurements. One unique way it varies from polyester is that while both cure quickly and easily. An epoxy cures with a hardening compound instead of heat; therefore, it can cure temperatures ranging from 5 t0 150 degrees Celsius.

Vinyl-ester resin:

Vinyl-ester resin is commonly a combination of sorts as it handles properties, falls, and characteristics between epoxy and polyester resins. Also, when referred to as a vinyl ester, this resin is formulated by esterification of epoxy utilizing a particular acid. This process formulated a resin that is superior to epoxy and polyester in thermal stability and corrosion resistance.

About polyester resin for FRP:

Polyester resin for FRP can be utilized to construct models, restore water ranks, make an artificial waterfall, statues shelves, sculptures, and build a bathtub. It is ultimately convenient to work with versatile and lightweight. It possesses good heat insulation, solid adhesive property, good light transmission, and good electrical insulation.

Additional details on FRP (Fiber-reinforced plastics):

FRP (Fiber-reinforced plastics) is a type of plastic that has been reinforced using a plastic material constructed of fiber reinforcement and polymer matrix. The reinforcement fibers may be basalt, asbestos, paper, glass, or fossil, and the polymer could be phenol-formaldehyde resins, vinyl-ester, or polyester thermosetting plastic. The procedure of step-growth polymerization or addition polymerization is typically used to create composite plastic.


Polyester resin is more commonly referred to as fiberglass or laminating resin. From the above-given information, it is understandable that Polyester resin for FRP is widely utilized because of its impact resistance, robust mechanical strength, and to keep a fixed shape of a finished product. However, we have come across its manufacturing process and learned that fiberglass comes in multiple shapes and has various types of glasses. And the accurate combination is concluded depending on the project.

Leave a Comment